Steel structural members constitute a structural system by means of connection joints, and the joint form has a direct influence on the structural integrity and reliability, the construction cycle and the design and construction of accessory members. According to the rotational stiffness, beams and columns of a frame structure are connected in a rigid, flexible, or semi-rigid manner.
At present, rigid connection is most extensively applied, and rigid joints for the beams and columns of the traditional frame comprise all-welded joints, welded-bolted connection joints, and bolted connection joints. It is discovered through research that the first two connection forms may cause brittle fractures due to the poor quality of welding seams at the ends of the beams and the lack of timely and effective protection in earthquakes; and the traditional joints are difficult to restore or reinforce after being damaged, and consequentially, the reliability of the joints cannot be guaranteed or material waste is caused.
As a novel earthquake-control structure, the self-recovery functional structure can guarantee the safety of people's life and property during earthquakes and can assist people in getting back a normal life as soon as possible after great earthquakes, thereby pointing out a new ideal direction for the earthquake-resistant design of structures. The self-recovery structural system primarily comprises a replaceable structural member, a swing structure, a self-recovery device, and so on. Research in recent years shows that the swing of the structure can reduce the influence of earthquakes and the requirements for the ductility of the structure, reduce earthquake damage, and reduce the manufacturing cost of the structure. The constraint between the structure and a foundation or between the members is released so that the structure can only be pressed, but not be tensioned on the contact surface with the foundation or on the contact surface between the members, and then the structure can swing in the earthquakes and can restore under the effect of a pre-stressing force, and in this way, a self-recovery structure is formed. The novel structural system can effectively control the maximum deformation of the structure and can reduce the residual deformation of the structure.
At present, many experts put forward the solution of arranging pre-stressed cables on frame beams of beam-column joints of a frame structural system to fulfill structural restoration after earthquakes, wherein short beam sections are connected with the columns through tensioning of the pre-stressed cables in a factory, only intermediate beam sections need to be assembled through all-bolted connection or welded-bolted connection at the construction site like common steel beams, and the pre-stressed cables do not need to be tensioned on site, so that construction is facilitated, the construction quality is improved, and installation time is shortened. However, self-restoration of concrete-filled steel-tube composite joint adopting high-strength steel bars between columns has yet to be researched and developed.